One type of data storage media utilize optical disks. In this type of data storage photolithographic techniques are utilized to form circular or spiral patterns on glass disks in much the same way as integrated circuits are formed on silicon wafers. The patterns consist of lines and spaces on which data may be permanently or temporarily stored. In the latter case the lines and or spaces may be formed of sensitive material on which lasers may be used to read, write or erase and rewrite. More conventional read, write and rewrite techniques such as magnetic read-write heads may also be used. A very important feature of such memory disks is the density at which data may be stored thereon. The storage density is a function of the closeness at which discrete lines and spaces are formed on the disks.